| Abstrakt: |
The re-discovery of a distal pluricolumnal of the Middle Triassic Eckicrinus radiatus requires separation of Eckicrinus from Holocrinidae and to establish the new family Eckicrinidae of undetermined systematic position. The pluricolumnal with enlarged radicular cirri with multiradiate articulations acted as a rhizoid holdfast. In the Early and Middle Triassic, three attachment modes occurred among benthic crinoids: (1) discoid or incrusting holdfasts (Encrinida, Millericrinida), (2) rhizoid holdfasts with radicular cirri (Eckicrinidae, Qingyanocrinidae), (3) motile cirri with synarthrial articulations (Holocrinida, Isocrinida). Encrinida and Holocrinida representing the two well known major clades of Middle Triassic crinoids are rooted in different Permian Ampelocrinida rather than in one Early Triassic common ancestor. Eckicrinidae may represent a third lineage. This evidence contributes to challenging the prevalent opinion that just one lineage of each of the five extant echinoderm groups passed the end-Permian extinction event. [ABSTRACT FROM AUTHOR] |
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